text:
How long does it take Boeing to develop an aircraft?
How long does it typically take Boeing to make a new plane model (e.g the 787), from the moment they decide to make a plane (the moment they decide to create a new 7X7) to the moment the first plane (in this case the first 787) flies commercially?

The answer to this question depends if you are focusing in a new airplane family (like the recent B787) or a family improvement that creates a new model in the family (B737MAX), or both

The only correct answer is probably "always longer than they thought", a simple consequence of the fact that research is almost impossible to estimate.

@JanHudec speaks the truth. In my experience, it's the unforeseen parts of R&D that take the longest.

For the general question, the answer will be "it depends on the aircraft." Specifically for the 787, though, the '7E7' program was officially announced on January 29, 2003. The program was later renamed to 787. It received its type certificate on August 26, 2011 and flew its first passenger revenue flight on October 26, 2011.
So, from the time the program began to the time of the first revenue flight was about 8 years and 9 months.
Of course, this is not including the R&D time invested on different projects whose R&D ended up being used either partially or completely in the 787 design before the 787 program itself began.
It should also be noted that not every airframe they start developing ever actually flies. Notably, Boeing worked on designs including larger 747 variants and the Sonic Cruiser (which would have cruised at Mach 0.98) before beginning the 7E7 program.
In addition to completely new airframes, aircraft manufacturers also commonly make derivative airframes based on existing product families. Current examples of derivatives in development include the 737MAX, A320neo, 777X, and A330neo ("neo" stands for "new engine option.") However, development time on derivatives can vary widely depending on how much modification is being made to the existing airframes and the level of resources being devoted to the project (which depends on market pressure.)
For a past example, the 2nd-generation Boeing 777 aircraft were announced on February 29, 2000 with the first aircraft, the 777-300ER, being certificated on March 16, 2004, and first service entry on May 10, 2004. This gives a time of about 4 years and 2 months from announcement to first service entry. This was likely slowed by the sharp downturn in aircraft orders following the 1999-2000 ".com bust" and, especially, the September 11, 2001 terrorist attacks in the U.S.
Also important is the FAA rule for applying for a type certificate. This will apply for new programs like the 787, but not for derivative programs like the 777X, which amend the original type certificate and do not need a new one. In 14 CFR §21.17:

An application for type certification of a transport category aircraft is effective for 5 years and an application for any other type certificate is effective for 3 years...

So once Boeing applies for a new type certificate, they have 5 years to get the type cetificate approved, unless they convince the FAA upfront that more time is needed. If the time runs out they must reapply, and the new type certificate would require the aircraft to comply with all new regulations passed since their original application.

You might need to add a few months between the CEO signing off on the decision to go ahead and the marketing people having everything in place to announce the program to the public.

So in the case of the 787 did Boeing have to apply for the type certificate twice?

@usernumber Apparently so. See the last paragraph of Section 1.1 of this document from the FAA, which says, "In accordance with the type certification process, the regulatory requirements applied to the B787 were those requirements in effect on the date Boeing applied for the type certificate as well as the additional amendments in effect on the date of Boeing’s request for a schedule extension."


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Who is India's equivalent of the FAA?
I frequently fly within India as part of my work and every time I am sitting in an airliner preparing to take off, I observe a lot of differences in each crew handling the take off or the ground crew procedures.
I would like to understand if there is any board that certifies these crews and airlines for safety, like the FAA for the US, if these information are released to the public, like a certificates that are issued for public information.

Welcome to the site! Your question is quite broad, is it possible for you to be more specific? You already mentioned the FAA, so are you asking about the equivalent body in other countries? Or how the FAA certifies aircraft? Or something else?

You are IN India, and are asking about airline certification for domestic flights in India, or you are asking about other countries and you just happen to be of Indian descent?

Yes for domestic flights in India.

This regulatory oversight is performed by the Civil Aviation Authority of a country. In India, this function is performed by the Directorate General of Civil Aviation (DGCA-India). Typically certification information is available to the public, but only high level information will be given.
Searching on the DGCA-India website I found this document that lays down the requirements on Cabin Crew Training.

source: Stack Exchange

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text:
How much should it cost to get IFR-rated? What to look for?
(Related to this question)
Many pilots have told me that an IFR rating is the most valuable thing i can do to improve my flying and margin of safety.
I know there are courses as quick as, "Get your IFR in 10 days!", but I'm unsure if that's  quality training that will stick with me.
How much should it cost for a robust, worthwhile IFR program for single engine land airplanes?
What would distinguish a worthy program from one that merely meets minimums?

The "Get your instrument rating in 10 days" courses seem to vary significantly: There's places where it's nearly all simulator time, and places where it's an intensive actually-flying-the-airplane training process (in actual IMC weather permitting). I wouldn't put much stock in the former, but I know a couple of folks who did the latter and felt it was great real-world training.

I don't doubt that it could be real-world training.  But I'm unsure how much it sticks with you.   "Flows" "habits" and "automatic actions" take time to develop.  I'm afraid that if it only took 10 days to learn, it may only day 30 days to forget. ;)

For the record, Rod Machado is of the opinion that accelerated courses are pretty good mostly because they provide high-quality instructors.

Back when I used to be a CFII, I noticed that generally speaking, there was a significant difference in the time it took for an older student to get an instrument rating than a younger student. There were exceptions, both ways, of course, but when an over-50 guy would come to me for an instrument rating, I always took care to tell them that they could become as good an instrument pilot as a 25-year old, but that the probability was that it would take more hours to do so.

The Part 141 flight school that I used to work at quoted around \$7,000 for their instrument package, which was 30 hours of dual flight, 20 hours of ground instruction, and 10 hours of PC-ATD simulator time. They were a Cessna Pilot Center using the old CPC King Schools course. It was a good course, and while numbers varied, I did have a couple of students who squeaked by right on the Part 141 course minimums. Other pilots added 5 to 10 hours more flight training into the mix.
In general, my gut says that it should cost an average pilot who has 100+ hours and flies semi-regularly between \$7,000 and \$9,000; probably closer to the low end than the high end, especially if the student does a bunch of self study at home on a flight simulator, possibly using VATSim as a simulated ATC.
As far as what to look for, I would recommend a Part 141 course just because the FAA is involved in the course standards, and instructor standardization is (supposed to be) part of the 141 criteria. It might be worth asking what their first-attempt pass rate is on checkrides, but that's not a meaningful long-term measure of the course's quality, just a short-term one.
You should find a course whose syllabus makes sense, includes simulator training and scenario-based flights, and make sure you work with an instructor you like. They can't be your best friend - they very well might need to give you some serious critique or cut a lesson short because things aren't going well - but you should be happy to spend a couple of hours a foot away from them in the cockpit.

I'm trying to track down the average hours to attain an instrument rating in the US; if I find it, I'll update my answer.

I agree with everything but the 141 part.  141 and 61 each have advantages and disadvantages.  Some of the best career instructors I know are part 61 only.

Unfortunately I don't have the full details any more of what I paid when I did my part 61 IR, but from what I can remember the costs are similar to the ones I listed in the other question you mentioned:

Aircraft rental
Instructor time (air and ground)
Materials (books, DVDs, charts, hood, timer etc.)
Written test fee
Examiner's fee for the actual test

If we assume a part 61 instructor (\$40/hr) and an IFR-capable rented aircraft (\$130/hr wet) then we come out with something like this (you need a minimum of 40 hours instrument time):

45 flying hours with instructor: \$7650
15 hours ground school (instruction and simulator time): \$600
Materials: \$600
Written test fee: \$150
DPE test fee: \$400 (plus \$130 rental for the aircraft)
Total: \$9530

Note that under part 61 you also need to have 50 hours cross-country PIC time, which I didn't include in this calculation. And I increased the materials cost slightly here, because IR materials seem to be more expensive than private pilot ones.
Key factors to consider are the instructor (as with any training) and the aircraft. A good instructor will help make sure things stick in your mind, even if the training is accelerated. I required 49.6 dual hours for my IR according to my logbook, but that was spread out over 10 months and I could certainly have reduced it by flying more often.
As for the aircraft, it's important to think about which aircraft you'll use your IR in, because training on a glass panel will probably be \$20+/hr more expensive than on 'steam gauges'.
Finally, you can make a lot of use of PC simulators like Microsoft Flight Simulator to practice instrument flight at home, which will be a lot cheaper than doing it in the air and it's surprisingly effective. Your FBO or flight school might have something more advanced, of course. And self-study in general will cut down on the ground school time you need.
I have no experience of part 141 or accelerated courses, so I can't say anything useful about those options but I would certainly research them if I was considering an IR. "Worthy" is a fairly subjective thing, but you can always ask around for recommendations, speak to previous students and so on.

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text:
What are good resources on causes of private aircraft crashes?
I'm working on getting my PPL, and I would like to read more about the specific causes of small private aircraft (single or twin prop, primarily) crashing, especially those that were caused by pilot error. Are there any good books or other resources on this matter? A decent amount of searching hasn't turned up much -- it seems like the data from private charter jets is often combined with that of the aircraft I'm interested in.

Let me start by saying that your idea is great! Learning from the mistakes of others is important, and anyone who aspires to be a better airman would do well to follow your example. I would suggest, however, that the causes of the larger aircraft crashes often offer excellent learning opportunities as well. Sure, some issues are type specific, but most will offer those great learning opportunities.

@JonathanWalters Yes, that makes sense. I suppose I'm looking for some sort of resource that gives detailed descriptions of the conditions leading to the accident and some insight as to how it should have been avoided.

Read this

Related question regarding NTSB reports

FAA interesting classification of GA accidents causes: Human Error and General Aviation Accidents: A Comprehensive, Fine-Grained Analysis Using HFACS. Related book.

The AOPA's Air Safety Institute has quite a few resources that I like to review from time to time, including some great videos with commentary on exceptional cases.
AOPA ASI Accident Analysis Page
AOPA Accident Case Studies
AOPA Real Pilot Stories
I do exactly what you are doing, during training and still after, but I'd like to also say that you shouldn't narrow yourself to GA crashes, a lot of what happens commercially can be applied to GA, and usually with commercial accidents there is a lot more data and analysis available to work with. In that regard, I like to watch shows on Youtube like "Air Crash Investigation", or on TV like "Why Planes Crash" (some available on Youtube)
AOPA also has a lot of resources to view NTSB reports on individual crashes where you can search by certain criteria like aircraft type, states, type of flight, or even some specific keywords like "Vacuum Failure".
Just don't limit yourself to looking at things like "Pilot Error", pilot error is a broad category of crashes that is usually used to describe the pilot doing something wrong in the air, but a lot of crashes are "pilot error" in that the pilot could have broke the accident chain much earlier in the flight. Read as many as you can, regardless of the cause. For example an accident where the aircraft breaks up in flight may not be attributed to pilot error, but its good to know what lead to the break up and what could have been prevented.

Exactly what I wanted. Also ordered "The Killing Zone" for further reading.

The National Transportation Safety Board investigates vehicle-related accidents in the United States and publishes "accident reports" which includes details of the accidents and the findings of the investigators. Go nuts.

Link to said NTSB Aviation Accident Reports database

Aviation Safety Network is another good place to look.


text:
What type is this aircraft with "inverted" wings?
A friend of mine saw this plane at Tampa Bay International Airport recently:

It has an odd combination of a negative dihedral and pylonless overwing engines, all traits I've seen individually but not together.
Does anyone know what this plane is, and what its purpose is?

Could be... the wings/engine were built or fitted in Australia?

Is it built by Pokemon?

If I am not horribly mistaken, it seems to be an Antonov 72 or 74, that were produced together, hence the similarity.
Another image (not included for copyright reasons) can be found here.
The wikipedia article classifies it as a "transport aircraft". It mentions a VIP transport variant and a maritime patrol one for the An72, several more variants are listed for the An74 version.

EDIT:
Flightradar24 lists only one An72 in the possession of CAVOK Air (thanks to bjelleklang for identifying the livery), registration UR-CKC.
The historical data indicates that this aircraft landed in Tampa on the 24th of May after a stop in St. John's on its way from Reykjavik.

It has an odd combination of a negative dihedral and pylonless overwing engines, all traits I've seen individually but not together.

Concerning the anhedral (the name of "negative dihedral") angle, you can find more info here, but we can summarize here that it has more to do with the high wing mount rather than the engine one.
The overwing mount of the engine contributes to reducing the risk of foreign object ingestion on unpaved runways.

Update:
The aircraft has been damaged beyond repair in a runway overrun accident occurred on Jul 29th 2017.

Wow! This was way more information than I was ever expecting! Thanks!

The forward mounting of the overwing engines, blowing exhaust over the upper surface of the wing, also contributes to lift via Coandă effect which helps with short-takeoff performance. https://en.wikipedia.org/wiki/Coandă_effect

An-74 is a special variant of the -72 for arctic operations, hence the similarities. The aircraft was designed as a tactical military transport for operation on short, unpaved, runways. The US had a similar aircraft around that time but it never entered production, the YC-14. The -74 was later built in more versions for military (and some civilian, probably military surplus) operators.

Looks like it could be a An-74 from CAVOK Air based on the paint scheme. There appears to be some in non-military ownership, but for this airplane it's difficult to say who owns it due to the low resolution.

In particular, Wikipedia says that CAVOK Air's AN-74 is operated under contract to the US Dept of Transportation, so this sounds pretty plausible.

Probably correct. While the lettering is hard to read, this seems to be UR-CKC and the text underneath the cockpit would say AN74TK-100

Seems like the aircraft is written off. According to Wikipedia: On 29 July 2017, Antonov An-74TK100 UR-CKC crashed on take-off from São Tomé International Airport and was damaged beyond repair. A birdstrike was reported and the aircraft overran the end of the runway whilst attempting to abort the take-off.


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What certificates/medical are required to fly in Japan?
I am FAA certified, but my medical certificate has lapsed. Would my pilot certificates and a fresh medical enable me to fly in Japan?

I don't know about Japan specifically, but generally speaking it's not that hard to transfer your licence between two ICAO-compliant countries, however you will need a new medical. Depending on what licence level you have there might be a theory exam and/or flight test required, but the hours you have count just about everywhere. If you get no answers here you should contact JCAB. But that's the first step, actually getting a commercial job is apparently hard for foreigners to Japan. You'll need fluent Japanese and permanent residency (so I hear).

Thanks for the comment Ben. Actually, I just want to get current again. There's a flying school near here that has 172's and I'd like to rent and go fly again.

I can't answer your question, but if you're anywhere near these guys then you could renew your medical and rent an N-reg aircraft from them. As a US pilot in a US aircraft, you shouldn't need any Japanese certification. At least, that's the way it usually works but they would be able to tell you if there are other requirements.

With a US license, you are allowed to fly US registered (n-registered) airplanes everywhere in the world.
Find a US CFI (in Japan) that can get you current and start flying.
The bigger problem might be, to find a Medical Examiner in Japan that is allowed to do medicals in Japan. My first search, at the FAA website (https://designee.faa.gov/SelectTypeOfSearch/SelectTypeOfSearch), didn't show anything.
Not sure if BasicMed works for you though.

This isn't universally correct. For example, in Europe, if you're a resident then you also need an EASA license to fly an N-registered aircraft.

@Pondlife That is not at all accurate. EASA does not have any authority to regulate issues related to a US pilot with a US license flying an N-registered aircraft. Residency has no impact on this. EASA cannot, for example, ramp-check an N-reg aircraft. That is why so many European pilots get US tickets and register their aircraft in the N-registry through holding companies.

@JuanJimenez See this answer and there's a lot of discussion on the web about it. But you may be right, it looks like the regulation has been delayed a few times, at least for private aviation.

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text:
Why did the pilot inform ATC that he is going to autoland?
I was listening to ATC and I heard the pilot say that they are going to autoland. What is the purpose of providing this info to ATC?

See also: http://aviation.stackexchange.com/questions/910/why-dont-pilots-always-use-autoland

So that the tower can keep the ILS critical area clear

From what you said, I'm assuming that the pilot had informed that he/she is going to autoland under VMC.
The main reason is that the autoland procedure requires accurate guidance and the ILS signals may be disturbed by the traffic (both surface and air). So, the pilots want to inform the ATC that they want undisturbed signal. From a Flight Operations Information leaflet from CAA, Qatar:

Most ILS installations are subject to signal interference by either surface vehicles or aircraft. To prevent this interference ILS critical areas are established near each localiser and glideslope antenna.
The ILS sensitive area is protected from all surface vehicles and aircraft when ILS Category II or III operations are conducted or anticipated.

These disturbances may happen when Low Visibility Procedures (LVPs) are not in force and may cause problems for the approaching aircraft:

When the LVPs are not in force, ILS beam bends may occur because of vehicle
or aircraft interference. Sudden and unexpected flight control movements may occur at a very low altitude or during the landing and rollout when the autopilot attempts to follow the beam bends.

Due to these reasons, it is better for the pilots to inform the ATC about their intention to autoland so that appropriate measures can be taken or if it is not possible, the same can be relayed to the approaching aircraft.

The ATC should be informed about the intention to conduct an autoland. Such
information should not be taken as a request for or expectation of the protection of the ILS but is merely given to enhance the possibility for ATC to inform the flight crew of any known or anticipated disturbance.

Also, the ATC has to adjust the aircraft spacing if autolands are being conducted, which may affect the operations.

Example #1. Example #2.

@TomMcW: Those remind me of some of my landings in Kerbal Space Program...


text:
Why was the WWII RAF fighter joy stick loop design not used widely?
WWII RAF fighters had a loop on top of the joy stick in case of hand loss or injury - Anyone know why the Allies didn't copy this very helpful idea?

I like to think the RAF were part of the Allies!

More than just Spitfires and Hurricanes. Bolton Paul Defiant, Westland Lysander, Hawker Hind, Hawker Tempest, Hawker Typhoon, Blackburn Roc, Blackburn Skua, Gloster Gladiator, Fairey Albacore, Fairey Barracuda, and others also had this control stick style.

A control stick with a loop at the top was called a "Spade Stick".  Generally only Hurricanes and Spitfires had them.
The cockpits on these aircraft were small and it was a problem for the control column to get full travel for roll control. This was solved by making the control column rotate at about mid-stick instead of from the the floor.
Other aircraft didn't use them because the cockpits were large enough to accommodate a normal stick and still provide good leverage and side to side travel.
The loop was there so a pilot could use both hands on the stick to get more lateral force since the effective length of the stick was now much less than a conventional floor mounted control stick.
Pilots found them to be much more comfortable to hold and loop style sticks did also get used some on larger aircraft with conventional floor mounted control sticks.
Full right aileron

Don't you enjoy the sharp edges right next to the pilot's knees? Ahh - British aircraft design at its best.

@Peter: The owner of the knees had a life expectancy of 4 weeks so  knee disconfort or injuries were perhaps not a major worry when those things were manufactured. Even today, given the chance, I'd love to sit in that seat.

@RedGrittyBrick: I know, they had a different attitude back then. Just the instrument arrangements in British planes was deadly already for some. But it's so  obvious - they could just had mounted the upper part on the forward side of the column instead the rear. I remember a parliamentary inquiry from 1947 why 10% of RAF pilots had died the year before (1946) in accidents. The answer was this would be normal. In peace time. What an attitude!

Interesting.  Yeah, I had always wondered about the strange control columns in Spitfires and Hurricanes.

@RedGrittyBrick funny how that same argument is often used in derision towards Soviet equipment.

@PeterKämpf care to elaborate on the instrument arrangement part? I can ask a separate question if you don't mind the callout.

I believe the other consideration not mentioned here is that the spade design comes from earlier wwI British designs like the se5a. So it was a carry over from those planes and the trainers like the tiger moth.
The spade facilitated two handed control. The early spits and hurricanes had no hydraulics (which were more costly to manufacture and viewed as vulnerable to failure from enemy flak and bullet damage). Control surfaces were strictly operated by muscle with cables and the modest leverage of the control horns, pullies and assorted linkage. In a dive or steep bank turn with g loads on the pilot it might take all you’ve got to pull back on the elevator.
Hence the observation made by another that heavier planes and multi engine (pilot co pilot) configurations get yolks in the American designs of the period.
The spade also allowed for easy switching of hands to access other levers, knobs etc mounted on either side of the cockpit without having to “let go” of the stick or pass it between your two hands as you would to get the same grip position on a straight stick.
By “allied” designs, I assume you mean American and many of our fighters except the earliest used hydraulics to control flight surfaces.
Oh and don’t forget that the Brits love to garden...so the spade was a familiar implement in their hands.

Would Polikarpov R-5/I-5/I-15/I-16 count?

I-16 panel. Source. Also photos of an earlier R-5.
It didn't have that peculiar half-stick roll, but it did have the "loop".
I can't say it was "copied" from RAF; after all, R-5 was designed in 1928, which predates most if not all similar British designs. Besides, Britain was not considered by the USSR an "ally" at that time (which didn't prevent them from using/licensing/copying British engines and perhaps other stuff).
Nor would I say it was done for the case of injury. It was just hard to control these airplanes with one hand.

I believe the Il-2 family and even is successors like the Su-6 and Il-10 also stuck with the loop design. That said, do you have any clue as to why did the loop fall out of favour?

I guess everyone adopted the convention we see today: agile airplanes get a (one-hand) stick, while heavier/less manoeuvrable airplanes get a yoke. If one is going to use both hands, yoke is arguably a more ergonomic design. That said, exceptions and mixed designs exist, such as central stick on the very heavy Tu-160, or the Tu-204 (or Concorde's) yoke which is not that fundamentally different from Spitfire.


text:
Why is the combustion temperature in a turbojet engine kept low?
Why the temperature of hot gas entering the turbine is maintained  far below the adiabatic combustion temperature?

Because there is no material to build a turbine stage able to sustain the combustion temperature?

Because the fuel-air mixture in a turbine is much leaner than what it would be for a stoichiometric combustion. It needs to stay lean to restrict the maximum gas temperature inside the engine - higher temperatures lead to exponentially shorter lives of the turbine components.


text:
Why does the boeing 747-8 have less wing flex than the 787?
If you know the 787 wing flex is much greater than the 747-8's wing why can't the 747-8 have a greater wing flex

related: http://aviation.stackexchange.com/questions/838/what-are-the-effects-of-the-boeing-787s-very-flexible-wings

The reason is twofold: The materials used and the high aspect ratio.
The 747-8 primarily uses advance aluminum alloys, while the 787 uses carbon composites.
The carbon composites flex more compared to the aluminum alloys. This can be achieved because the carbon fibers are anisotropic and their properties can be tailored in each direction.
The yield strain of the aluminum alloys used in aerospace is ~1%, while that of the carbon composites is about 50% higher, ~1.5%.
These material characteristics mean that the carbon spar can flex more compared to the aluminum one. This effect is magnified by the high aspect ratio of the Boeing 787.
The aspect ratio of the 787 is about 11 while that of the 747-8 is about 8.5. This means that the wings are more slender and flex more for the same load.
The 787 wings are able to take this flexing in part because of the excellent fatigue properties of the Carbon composites used. See this question for a very good discussion on the causes and effects of wing flexing in 787.


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What are the advantages of the B747-8 airfoil over B737's airfoil?
The Boeing 747-8 has a new airfoil design much different than a Boeing 737's airfoil.
Boeing 737 airfoil:

(source: How Airplanes Fly?)
Boeing 747-8 airfoil:

(source: Boeing)
I am a little confused of why it is shaped like this. What are the advantages of this new profile?
It is also more thin, wouldn't that reduce the amount of fuel stored in the wings?

Why don't you compare it to the old 747 airfoil? This is like asking why an apple isn't segmented like an orange. Different designs have different goals and efficiencies!

Your picture shows some generic airfoil, but certainly not that of the 737. The 737-NG and 747-8 airfoils don't look very different.

The airfoil profile you've shown is called a supercritical airfoil.
Typical airfoil sections are curved on the top and the bottom. The airflow over the top of the airfoil is accelerated i.e. the airspeed over the top of the airfoil is more compared to the free stream velocity. The associated reduced pressure helping to create lift.

Source: www.symscape.com
From the figure, two things can be inferred:

The pressure over the upper surface is lower compared to the lower surface
The pressure gradient is favorable in the forward section of the airfoil (where most of the lift is produced), while the gradient is adverse in the rear half, which can cause boundary layer transition and possibly separation, if the gradient is too severe.

Source: code7700.com
For low speeds (and low angles of attack), this causes no problem in lift generation. However, most of commercial airliners fly at in the transonic regime (with speeds ~ Mach 0.9), the flow over the top of the wing may reach supersonic speeds even when the aircraft itself is flying at subsonic speeds.

Source:fluid.mech.ntua.gr
The speed at which this happens (flow over wings becomes supersonic) is called the critical Mach number. The flow decelerates through a normal shock wave, resulting in a severe adverse pressure gradient over the rear of the airfoil.

Source: fluid.mech.ntua.gr
This causes serious problems like:

The adverse pressure gradient over the shock wave causes flow separation, decreasing lift and increasing drag. The speed above which the drag increases significantly is called the drag divergence Mach number

Source: history.nasa.gov

As the speed increases, the shock wave moves to the rear, as does the lift producing region. This causes a nose down pitching moment and stability issues.

"Transonic flow patterns" by U.S. Federal Aviation Administration - Airplane Flying Handbook. U.S. Government Printing Office, Washington D.C.: U.S. Federal Aviation Administration, p. 15-7. FAA-8083-3A.. Licensed under Public Domain via Commons.
The supercritical airfoils are designed to overcome (or delay) these problems. Designed by Richard Whitcomb, the main characteristics of these airfoils are,

'flattened' upper surface
highly cambered aft section
smaller leading edge radius compared to the traditional airfoils (that is why they are so thin)

Source: aerospaceweb.org
The main advantages of supercritical airfoils are,

It increases the drag divergence Mach number. For example, in the F-111, the drag divergence Mach number was increased from 0.76 to 0.88, a 16% increase.
The shock waves are developed further aft when compared to the normal airfoils
They greatly reduce the shock induced boundary layer separation, reducing drag

The figure below shows a supercritical airfoil in a transonic flow. Note the location of the normal shock compared to the 'normal' airfoil.

Source: space.bas.bg
The supercritical airfoils were not available when the Boeing 737 was first designed. However, the 737 NG airfoil incorporates elements of supercritical design,as does the Boeing 747-8 airfoil.
The supercritical airfoils reduce the fuel required, as they allow the aircraft to cruise at higher speeds with lesser drag. Additionally, the Boeing 747-8 has a wing span of ~68 m, which gives plenty of storage space for fuel. Also, improvements in engines and airfoils means that the 747-8 has nearly 50% more range compared to the original 747-100.

The leading edge radius of a supercritical airfoil is bigger than that of a conventional airfoil, which gives them a higher $c_{L_{max}}$ as a nice side benefit.

So the (b747-8) airfoil is designed to reduce wave shock drag

Yes, to delay the onset of wave drag.

Some things to keep in mind when comparing two very different planes:
The 737NG is the latest version of the 737, and it was designed in the 90's. The design changes included a new wing. The 737 is designed for short flights, with a top range of about 3,000 nmi. The 737 has a design cruise speed of about M0.78.
The 747-8 is the latest version of the 747, and it was designed in the 2000's. The design changes also included a new wing. The 747 is designed for long flights, with a typical max range of 7,700 nmi. The 747 has a design cruise speed of about M0.85, and is much larger than the 737.
So the two planes span at least a decade, and are optimized for very different profiles. The 747 will be optimized more for cruise, and at a higher speed. The 737 will be optimized less for cruise and more for shorter segments.
Another point is that the airfoil is not uniform along the wingspan. As the 737 link shows, the airfoil shape will change along the span.
However, the two flight profiles include cruise speeds of around M0.8, which means that both planes will be optimized with a supercritical airfoil, as is explained in another answer. Therefore both airfoils will have much more in common with each other than compared to, for example, an aerobatic plane. I'm not sure where you got the idea that your first image is a 737 airfoil. The source site just says it is typical for a "stunt plane", which the 737 is not.


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Is there a NOTAM code for solar eclipse?
Sun eclipses have some noticeable effect (e.g. drop in air temperature). Inspired from Eclipse Flights (xkcd) I'm curious if eclipses are notified as NOTAM or as weather notice. How?
Never seen such notification (but there are also few sun eclipses).

For whatever it's worth, I live in the totality path and the airport I fly out of (which is almost exactly in the center of the totality path) does not yet have any NOTAMs issued for the eclipse. The nearby major airport (also in the totality path, but not quite as close to the center) doesn't have one, either. It's still 3 weeks away, though, so that's not to say that they definitely won't issue one later.

Anyone flying under VFR might be more concerned that it goes completely dark for a couple of minutes, than by a temperature change! Any temp change wlll be very dependent on the wind speed and direction. Also, the speed at which the light increases can be too fast for your eyes to comfortably adjust (personal experience observing a couple of solar eclipses from the ground).

I live in the totality path (totality occurred here about 45 minutes ago.) I don't see NOTAMs for the eclipse at any of the nearby airports, including one whose runway is about 1 mile from the center of the totality path.
While NOTAMs may be issued for traffic purposes as ymb1's answer points out, it seems that there's no general requirement for a NOTAM to be issued for airports in the totality path.


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What is the benefit of having baro-VNAV in addition to a WAAS GPS?
On Cirrus' 2015 aircraft page, they advertise Baro-VNAV capability in the new model. Having never done an LNAV/VNAV GPS approach (only LNAV or LPV), I'm wondering: when would I actually use it, if I already have WAAS and can just use the LPV approach? Typically, I'm used to seeing an LPV minima alongside any LNAV/VNAV minima. Are there exceptions? Is this feature valuable in practice?

LPV and non-baro LNAV/VNAV requires that a Space-Based Augmentation System (SBAS) be available to the GPS receiver.  In the United States, that system is called Wide Area Augmentation System (WAAS).  Similar services operate in other parts of the world (e.g. EGNOS in Europe, MSAS over Japan, GAGAN over India) but coverage is not worldwide, and not all GNSS (Global Navigation Satellite System) approaches are approved for LPV.
Having a baro-VNAV system in the aircraft allows you to shoot LNAV/VNAV approaches if SBAS is not available. While not as useful in the United States, as we have robust and reliable coverage with WAAS, it is nice to have in parts of the world where SBAS is unreliable or non-existent.
FAA fact sheet on RNAV (GPS) approaches: http://goo.gl/cIhIJa
Worldwide SBAS information: http://goo.gl/eooOau

Baro-VNAV computes vertical navigation based on barometric pressure, rather than on GPS-based WAAS altitude.
The altimeter feeds digital altitude information into the RNAV/VNAV unit, and the RNAV/VNAV unit provides vertical navigation information to the pilot by computing a synthetic glideslope, to guide the airplane from the FAF down to DH above the runway.
One major factor for Baro-VNAV is temperature, which cannot be set in the Kollsman Window of the altimeter, so these approaches have a minimum OAT at which they can be utlized.
Reference: RNAV (GPS) Approaches


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Why do many light aircraft have a trim tab on one side of the elevator only?
Most light GA aircraft, like this C172, have pitch trim tabs on one side of the elevator only. Why not on both? Doesn't the asymmetry add inefficiency in the form of a slight rolling moment?

A small propeller driven plane like that will have a bit of adverse yaw, rolling to the left, because of propeller effects (P-Factor, slipstream, torque, etc)
The trim tab's effect is minimal because it is very small and is close to the centerline of the plane.  Any drag it creates causes a slight roll and yaw to the right, specifically to counteract the propeller effects.
That keeps the overall effect almost un-detectable.

It doesn't always roll to the right, when you have it trimmed up the trim tab will be angled downward and give you a roll to the left.

I agree, it wouldn't always roll right. But the fact that it is placed on the right is a good point. Regardless of roll, the (small) added drag on the right side could help counteract the aircraft's natural left turning tendencies.

The tab is on the left of citabrias.  Presumably the effect is so minor that it doesn't even matter what side it's on?

@KirkWoll: What does “citabrias” mean?

Citabira means "airbatic" backwards.

It's a type of light aerobatic plane.  Here's a picture with the tab on the left.  http://i759.photobucket.com/albums/xx233/superjuice90/citabria3.jpg

@KirkWoll No it matters what side the trim tab is on, you want to counteract the adverse yaw created by a prop not add to it...I'm not familiar with the Citabira but I'd wager a guess that the prop spins counterclockwise...or that there is some asymmetry in the body

@spacegirl1923, I believe you are confusing the pitch-trim with the one on the vertical stabilizer.  This question is about the former.

@KirkWoll no I'm talking about the pitch-trim, but let me clarify to say adverse effects of the prop in totality...  I could explain but this already says it well...https://www.quora.com/Why-is-the-elevator-trim-tab-on-a-Cessna-Skyhawk-on-the-right-side-only

@spacegirl1923, the citabria is a perfectly normal plane that has all the usual left-turning-tendencies. I don't think it's location on the left or right makes any difference.

That is a really good quora explaination, @spacegirl1923. It covers some aspects not in my original answer. Thx.

@KirkWoll given how quickly you responded I know you didn't read the link I posted...

@abelenky I agree and no problem!

Well, the fact is it's on the left of a citabria, and it spins clockwise, and is not in any other way assymetrical.  ¯_(ツ)_/¯

The reason the trim is only on one side is cost saving; one trim tab is cheaper to build and simpler (therefore cheaper) to maintain.
As for the rolling motion yes, the trim tab will cause a slight rolling motion. Very, very slight to the point you won't detect it for the following reasons:

The trim tab is small. Compare the surface area of the trim tab to the aileron, there just isn't enough of it to make much difference
Small lever arm: the ailerons are positioned far out on the wing so they have a longer lever arm, this decreases the force required to roll the airplane across the longitudinal axis. The trim tab is located almost on the longitudinal axis, so will have very little leverage

Wouldn't most of the (minimal) torque produced by the trim tab also be counteracted by the pilot typically sitting in the left seat? (at least, in a single-user configuration)

The effect is so minimal I don't think it's a factor. There's plenty of airplanes that have it on the left, it's more of an engineering question.

Besides the aforementioned cost, consider how the additional unnecessary complexity can add risk to the free movement of the elevator and rudder, should problems occur with its linkages.

It's all up to costs, in a sense. A more complex mechanism is more costly to realise if one wants to achieve the same level of safety and flawlessness as a simpler one.


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Why don't commercial jet aircraft have a break-apart, parachute escape system?
Imagine that the pilots on a jet aircraft determine that it will crash. Consider what would happen if the design of the craft allowed it to:

Break into four pieces
Each piece is pressurized independently
Each piece is attached to large parachutes, similar to how they bring down Soyuz or other space crafts returning to Earth

Would that not work so that passenger jets are brought down safely instead of crashing?

Hello Corey, welcome to aviation.SE. You certainly have a creative mind, I am not so sure the idea is realistic. Aviation is somewhat weight-critical so this seems an expensive design change don't you think?

Although I can see why this seems a silly question and is being down voted, I'm up voting due to the fact this has clearly been thought about and isn't just a random thought. The fact it's not practical doesn't mean it isn't worth asking

Random thoughts are awesome. Like "I wonder if I was racing along at the speed of light, could I reach out to a light beam beside me and touch it?"

This is a valid question that I have heard asked many, many times. For those posting on this site the answer is obvious (weight, and go name any particular incident in which it would have helped) but for the naive public it seems like a logical aviation accessory.

@MikeyMouse Feel free to ask that on [physics.se]. I'm already pretty sure of what the answer will be though.

@Ajedi32 It's already been asked an answered 100 years ago, I just wanted to use it as an example of why Random thoughts shouldn't be discouraged.

There was a design proposal almost exactly like this called "Keyse's Supersonic Detachable Wing" in the Great International Paper Airplane Book from 1967:  https://www.scribd.com/doc/53007352/Paper-Airplanes#page=45

This is silly.  It would be easier to have a small "life-jet" attached to the plane and people would simply slide over to this jet if the big one had a problem.

@MikeyMouse Random thoughts are great. Random thoughts posted as questions on SE sites without even the slightest hint of cursory research first are not. I mean... "equip airplanes with giant parachutes", first result answers the question entirely. Or whatever other similar sentence you want to type into Google.

@MikeyMouse Has it been 100 years already? How time flies.

http://aviation.stackexchange.com/questions/11584/why-movable-thrusters-are-not-used-in-airplanes/11589#11589

I don't see why pressurization is necessary - as long as the decompression is not explosive (let's say it should take more than 10 seconds), your compartments are going to plummet fast enough to avoid loss of life due to oxygen deprivation. Especially since oxygen masks are already the standard.

See Why a detachable cabin probably won't save your life in a plane crash

This idea would be as complex as building the space shuttle

@Gabe Would it not be worth the effort if it saved lives?

Though the phrase says when referring to the value of a soul "one life lost is one too many", unfortunately there is also a economic reality. Building an airliner is already expensive, complicated, and long process(from design to certification). I can barely grasp all the implications of making something like this a reality. The only way I see this possible in a practical way(both in the economic and construction sense) is if some new way of building aircrafts is invented(faster and cheaper), also it would need a lot of support from the regulation side(approving a new aircraft design is slow)

wouldnt that work for keeping a majority of passenger jets from crashing?

The majority of passenger jets don't crash.
Designing an aircraft like that would incur very substantial weight penalties. The Space Shuttle booster rocket parachutes weight 990kg, each (it needs 3) plus 550 kg for the drogue chute needed to pull out the main canopies. Plus another to pull out the 550kg drogue. Where are you going to put that much nylon?
Then there's regular maintenance of stuff that large and heavy - you will need an entire empty hangar to repack things along with a crew and a crane.
Also consider how you are going to break up a commercial airliner in an orderly manner. It would have to be designed for it and lined with explosives. That's going to be really popular.
Finally, parachutes need time to work. Large parachutes need considerable time. So this whole process only helps if there's a problem in cruise flight, and that's the phase with the lowest accident rate. Parachutes below 1000 feet are just excess weight.
Semi-related Addendum: After Challenger went boom the Space Shuttles were fitted with a crew escape system. It was intended to allow the crew to exit when the craft was under control but unable to reach a survivable landing site. Re-read that carefully: when the craft was under control. The crew exits at reasonable altitudes and the Shuttle crashes under remote control.
Parachutes simply haven't been a viable option for commercial air transportation since the DC-3 era.

In addition to the chutes there's also the substantial weight penalty of three separate sections of the fuselage with independent pressurization (or at least pressure retention): Pressure bulkheads are extraordinarily heavy. Pressure doors would have to be installed as well, and kept closed during flight (there goes food/beverage service), automatically closed in the event of separation (more weight!), or each section would need separate boarding and dedicated cabin crew (more money!).

nice answer, I retracted my close vote and now hope you will be the first to get the reversal badge :-)

Furthermore, aircraft manufacturers use similar patterns from one model of plane to the next, and this "escape plan" would likely require to design a completely new plane, resulting in high conception costs.

Also, I'd assume the body of the plane would have to be much stronger to survive being braked by the parachutes. All those extra masses and costs add up really quickly. It's like rocket science-lite :D

Much stronger. I've been under 26-foot personnel parachutes when they open. It's not pleasant.

You forgot the most important part - the passengers themselves would have to be strapped in and probably using something more than a lap belt considering the force of impact when the whole chunk is separated, the pyros fire to launch the chute, and then the force when the chutes finally deploy.

Can you imagine the expense of disassembling the airplane periodically for parachute repacking and explosive inspection?  Inspections are already expensive, having crack the whole airplane into pieces for a full inspection of those parts would be crazy.  Nevermind all the extra points of failure being introduced.  Not a bad idea for small airplanes though (Cirrus does it), but it has problems to overcome before scaling up.

"The majority of passenger jets don't crash." LOL!! Talk about an understatement. :-) Brilliant opening to this answer.

DC-3 era? Is there some back-story here involving DC-3s and parachutes? ;)

The plot twist here would be that the extra weight and space of arguing parachutes would mean we need more flights, meaning more accidents and likely more deaths overall

@JeffBridgman In the DC-3 era some passenger seats were made with parachutes built into the cushions (proof-of-concept, not commercial). 3 buckles, stand up -> you're done. And it's easy to jump out of a DC-3, I've done it a couple of times.

Paul's answer covers the main points (difficulty, expense, weight); I want to flesh out the rarity of use aspect.
As Paul says, most accidents happen during take-off and landing, when the system is useless because the parachutes wouldn't have enough altitude to deploy. The only time you'd be able to use this system would be if you were flying at a decent altitude and you knew in advance that the plane was going to crash. This almost never happens. Perhaps parachuting to earth would be a better option than trying to ditch a plane on water, especially over the ocean, but ditchings are very rare. Otherwise, unless there's been some mechanical failure that makes the plane uncontrollable, an emergency landing is probably going to be a better bet, even if all your engines are out and you have to glide – and a large passenger plane can glide for 20–25 minutes from altitude. In most circumstances, an intact plane can fly a decent distance and it would be very, very dangerous to turn any kind of flyable plane into a collection of free-falling components.
Indeed, the proposed system would be useful in such a tiny fraction of air accidents that you'd probably find it causing more deaths than it prevented. You're talking about fitting tens of thousands of planes with probably hundreds of explosive charges each. How many maintenance workers are going to be killed by how many accidental detonations? How many times is it going to fire accidentally in mid-air due to, say, a small cabin fire in just the wrong place or a lightning strike?

Some numbers you may want to add: an average plane (say a 747) can glide for about 93 miles from it's cruising height of 33k feet without any engines.

Part of what I was worried about was mis-firing of deployment. At a few million flights/year, there's bound to be a few airliners landing in someones backyard.

The take-off and landing crash scenario could be solved with a giant air-bag deployed under the aircraft by a cockpit button just before impact.  A bit like a stunt crash-mat.  Or hundreds or thousands of smaller ones, arranged in layers.  I'm sure all the same weight caveats apply but I reckon it might get used more often than parachutes.  Just a random crazy thought inspired by the original question.

@EdRandall The (im)plausibility of that idea is a separate question.

Even in small aircraft, would there be any at-altitude problems that would necessitate parachute deployment that would be anywhere near as common as pilot incapacitation or freak loss of visibility--both issues that would be essentially irrelevant in an IFR-equipped airplane with a copilot?  In a single-pilot aircraft which is not equipped for IFR, I would think a parachute system would serve mainly to guard against problems that are simply irrelevant in larger or commercial aircraft.

I want to comment on the 'break apart into 4 sections' comment.
If your 4 parts were two wings, tail and the pressurized portion, thus reducing the weight that needed to be lowered safely (and removing some of the problems that Paul pointed out), you still have one major problem:
You've just designed a plane that has a way to specifically remove its wings in flight.  This would be a terrorists's dream ... no need to bring their own explosives if they can hack into the control systems (don't even need to disable the parachute deployment, if you can get it to trigger when the plane's low enough, like while it's coming in for a landing ... or on takeoff, so it throws lots of fuel at the same time)
...
but I will mention that there do exist whole-plane parachutes, but they're for much, much smaller planes.  (and they claim they only need 270' as they're rocket-deployed, so no drogue chute needed)

This was my first thought and I did not even think of the issues everyone else is concentrating on.  If we are thinking outside the box why cant we pack a small ultralight aircraft in our airplane.

@emory How are you going to save a few hundred passengers with one small ultralight aircraft?

@DavidRicherby By taking multiple trips, of course.

@GhillieDhu Is that a joke? "Multiple" would mean "a hundred or more". If you have time to do that, you have time to fly across an ocean to find an airport to land at.

Yes, it's a joke.

...and there are (again small) planes designed this way from the beginning: http://cirrusaircraft.com/innovation/?item=parachute#innovation

@DavidRicherby: Suppose the airliner has an engine failure and can't move under its own power. A small plane that could evacuate the passengers a few at a time might be cheaper to provide than a rescue plane strong enough to tow the entire jet.

@HenningMakholm You have 20-25 minutes max before the failed plane hits the ground and a few hundred passengers to evacuate. If you your rescue plane holds a few people, it's going to take about 100 round trips to empty the plane. That's a round trip every 15-20 seconds.

And here is live case of whole-plane parachute with picture http://abcnews.go.com/US/wireStory/police-plane-helicopter-collide-maryland-26408833

@DavidRicherby You only have to evacuate those that have paid for 'Premium first class',  capitalism at its finest.

It's been done, but it was a major engineering feat just to do it with a four-person crew capsule.  Ejecting sections of the passenger compartment of a commercial airliner would be even more difficult.  As others have noted, it would significantly increase the cost and complexity of the aircraft and decrease its payload for very little improvement in safety.
Here is footage of the B-1b Lancer crew capsule.

Isn't that a B-1a? The crew capsule design was replaced by ejection seats on the B-1b.

Any time the question is "why don't we have...", the answer is almost certainly in the trade-off between weight, maintenance cost, fuel cost, & utility. If it weighs a lot, needs maintenance, burns fuel, and will only be useful once a decade, then it just is not productive.
Putting a complex break-apart & parachute system on a plane will be heavy, meaning fewer passengers, or less fuel or cargo on board. All that extra weight has to be flown around, requiring fuel. They would need regular maintenance checks, which is another cost. And they would only be useful very, very infrequently (on most planes, it would never be used).
So it is just impossible to justify adding new equipment for a once-in-a-lifetime scenario, which can be better managed with good maintenance, good training, and good planning.
This same line of reasoning goes for "why don't more airplanes have rocket thrusters", "why don't planes have anti-missile systems", "why don't planes have airbags", and many other random items.

Parachute rescue system is available on smaller airplane, like Pipistrel Panthera, and latest Cirrus SR22/SR22T. Your scenario looks nice, but probably not practical enough to be installed on larger aircraft.

Hello Spidol Pulpen, welcome to Aviation.SE! Indeed parachute systems exist for smaller aircraft but not for larger aircraft. Could you please expand your answer and explain why it is not a practical solution for large aircraft. That would improve the quality of your answer.

Also note that Cirrus aircraft since their very beginning have included parachutes. It's not restricted to the "latest" ones.

Getting past the boring part about cost and how it's inconvenient and impractical, there's still a lot to think about.
I haven't seen anyone mention this but four separate pressurized parts of a plane has to be one of the most complicated parts.
It will be like a subway system with multiple cabins. This sounds simple enough when pressurization is not accounted for. There are three major factors against this design.

Weight - There'll be a lot of connection, multiple redundant systems, more insulation. This means less passengers and less fuel onboard.
Size - It's gonna be much bigger, there's a lot of mass and that takes space
Cost - All this equipment and systems take money to add, self explanatory.

Another requirement would be a door between each part of the cabin would have to be similar to the emergency exit door.
At this point you might as well just have four small planes that each have parachutes. This is the best way I could think of doing it and really the only way (I could think of) but I would love to hear how else it could be done.

I've had a few chats within the business on this subject in light Ballistic Recovery Systems airframe parachutes developed for light, single engine aircraft.  The consensus seems to be 1) weight -  heavy equipment uses up useful load 2) added cost to buy and maintain 3) not necessary due to the redundancy in multi-engine aircraft 4) as earlier pointed out, most accidents happen during t/o or ldg where the a/c is too low for a successful deployment.

Cost. That's it. Human life does have a cost associated with it. Its ugly to think about, but of course we have the technology to do something like this.
Extra parachute systems would weigh more- and that dead weight has a cost in gallons of jet A, maintenance, life cycle and all the other things that go on the other side of the balance sheet. The aviation manufacturers build the planes their customers want- and their customers don't want to pay for the additional product maintenance life cycle cost of an extra couple tons of safety equipment.

I forget which incident triggered it, but I recall some years ago that an inventor and his invention (for which he sought a patent), proposed to do almost exactly this, and was featured on a news story. The inventor felt that he was being brushed off for no good reason.
However, then as now, it's an unfeasible idea for numerous reasons including cost, weight, reliability, and insignificant or non-existent window of opportunity for effective use.
Consider: in exactly what sort of scenario could such a system actually offer a favorable outcome? How would it be determined that activation of the system is the correct action? If so, what preparation within the cabin would be needed pre-activation?
Bad things happen very rarely, extremely rarely at altitude (where any sort of parachute system would have a chance of deploying effectively) and happen without warning. By the time the emergency is recognized, it may be too late to push the button on such a system.
Another point: it is always better all around to prevent an emergency from ever occurring than it is to develop systems to be activated in response, especially when the response is as complex and expensive as a break-apart and parachute system.

The bottom line for most operators is that modern airplanes simply don't crash.  In the West, the probability is just about zero, so no emergency devices like this are needed.

Are you aware of any stat or just create this account to try to be funny?

@vasin1987, the last fatal crash of a US airliner was in late 2001.

@mark thanks for info. Implying West is more safe is too broad. Remember AF447? There are a lot of East airlines with great reputation. Try SQ or CX. By the way if you consider frieghter as well, the revent one is UPS1354 in 2013.

If you're not familiar with commercial aviation, you may feel justified in responding in an abusive manner.  But that just speaks to your inner urge to be a public spectacle.  Consider 2014 as an example: there were 18 fatal airliner crashes in places such as Nepal, Malaysia, Iran, Algeria, Ethiopia, Indonesia, etc and NONE (ZERO) in North or South America, or Europe.  There is a reason for this, and it's nothing to do with a lack of parachutes or other irrelevant devices. Bring facts; it's no help to anyone here if you just pop off with irrelevant remarks.

An airliner travelling at over 800 kmph could never have a chute safely deploy in mid air... the design of such a thing wouldn't be possible. The strings, however synthetic, whether carbon fiber or whatever else would never hold to such pressure. Furthermore, the jolting force of have a chute deploy even at the minimum required flight speed of your average commercial jet, let's say 250mph would jolt passengers to the point of serious injury.

Apollo and other spacecraft managed it.  The trick is to use staged parachutes, and possibly staged opening of parachutes.


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What is this weird plane?
Can anyone identify the make and model of this aircraft? I'm just really curious.

From what I can tell, it's a Burt Rutan design. I then searched and it appears to be a Rutan Defiant.

I was initiall guessing a Starship, but I think you're right.

No, Starship is twin pusher, but it's also a Rutan Design.

@keshlam and the starship has smaller canards

@keshlam and is quite a bit larger

Good points, all.


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Can civilians fly military aircraft?
I saw a few videos of the Sukhoi Su-35 doing some amazing aerobatics and I was wondering if a civilian could ever fly one - either for aerobatics or just fly it as their personal jet.
Obviously assume adequate training, fitness, budget, time etc. I assume you'll have to start on a jet trainer first, after you had already flown other smaller aircraft - but this is outside the scope of my question.
There is a question that suggests civilians can buy military aircraft, but it doesn't explicitly say whether they can actually fly them. One comment seems to suggest they can't, although it's not very clear.

you wouldn't be allowed to have active weapons most likely but beyond that they are normal planes

It's possible it may differ in certain countries; are you asking about in the US?

@DannyBeckett Not necessarily. I'm not thinking of a specific country. I wouldn't mind an answer about the US.

Go to http://www.globalplanesearch.com/usa/warbirds/combat/ and buy one.... :D

I know this is older, but see http://flyin.airventure.org/news/2010/100407_harrier.html

I don't see any comment suggesting they can't fly them. Only answer that no F-14s were left in flyable condition after decommissioning, but that had a reason specific to that type.

I could see perhaps flying with an instructor in the rear, but to own and fly solo your own fighter jet?  Sounds like a bureaucratic nightmare... Surely you would need some sort of type rating, and that would mean being signed off by someone qualified which, in this case, would also have to be an accomplished military jet pilot instructor.  Here in Canada, even military fighter pilots in training have to fly under restricted G-load until they've passed a rather gruelling spin in a centrifuge (to make sure they won't G-LOC and ruin everyone's day...)

This was actually answered on the other thread. You can fly a jet fighter if someone owns one and lets you, for example a company like this http://austjetadv.com.au/strikemaster_packages.html that I linked in my answer there. That doesn't mean you can fly it however you want, though, so even if you owned a high-performance fighter jet, you might end up feeling a bit like a high-performance car owner on public streets in the USA.

I'm not sure if you're asking about flying such an aircraft (e.g. renting one) or owning one. But either way the answer is yes.
I've flown a Hawker Hunter at a (now-defunct) location in Cape Town on a mixed low-level/acrobatic flight along the coast. There were no restrictions on who could fly in the aircraft apart from the obvious ones (no kids; must have reasonable height/weight and general fitness) but they didn't let non-pilots take the controls. We did some aerobatics (up to 5G, from memory) and I had the controls in cruise flight for about 10 minutes. There was absolutely nothing that a civilian couldn't learn: it's 'just' another aircraft.
As for owning one, it's not uncommon at all. Privately owned ex-military aircraft are often referred to as "warbirds" and in the US there's even an EAA organization for owners. The aircraft are usually considered experimental (or the local equivalent) for the purposes of regulation and airworthiness.
The barriers to owning these aircraft are (as always) money and training. Buying and maintaining them is very expensive because there are so few parts or mechanics available, and insuring them is (almost) impossible so most owners have to self-insure. The operating costs are also usually high, especially if the aircraft systems need 'exotic' fuels, gases, lubricants or other consumables. You may need to include explosives on the list, in the case of ejection seats.
Training is a similar issue because so few people can instruct you in how to fly a military aircraft, but obviously this isn't a total barrier and I assume that if you're involved in that part of the flying community then you'll find the contacts you need.
So in general, if you can buy a military aircraft legally in your country, if you have enough money for operations and maintenance, if you can find someone to train you, and if you can comply with your local regulations on non-type (experimental) aircraft then you can absolutely do it. But for most people that's a lot of 'ifs' :-)

I have flown an L-39 military trainer that a local FBO was renting time in.  Lots of fun, but not something you want to fly any distance.    This place will give you an orientation ride and work with you on getting your LOA if you are interested in buying and flying a jet warbird. There also was an outfit in one of the former Soviet countries that would give your rides in more modern Migs like the Mig-29.

I've flown the L-39 with JetWarbird, as well

The test pilots of military aircraft manufacturers are also civilians flying military aircraft. They perform among others checkout flights before delivery or after repair of every single military aircraft. Usually they are former military pilots.

Yes, civilians can fly military aircraft including jets.
The Czech's have sold off a lot of their old L-39 trainers and you frequently see them around airfields. I know of one accident where the L-39's nose, which normally carries a radar, had been converted into a luggage compartment and the hatch opened as the guy was taking off and one of his suitcases flew into the left engine with fatal consequences.
The biggest headache is the ejection seat which is a maintenance nightmare with various legal issues. Also, military jets tend to burn fuel like a son-of-a-bitch, so they can be expensive to fly.
One of my dreams is to someday own a Texan, which would be so cool (think: cruising at 300 knots, wowzers!). Hopefully, Greece will go bankrupt and have to sell off all their Texans cheap, hee hee.


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What does it mean for a payload to be "caged"?
If an aircraft has a movable payload (e.g. camera) attached to it, two of the status modes are caged and stowed.
Stowed indicates the payload is retracted and or in a locked position.
What is caged?  I have found reference to "caged" in a couple of resources online, but the do not explain the term.  In some documents about passenger aircraft, it refers to cages in the luggage compartment, but this is completely different.

I've always understood caged to mean fixed, as in the gimbals aren't moving. Like uncage the attitude gyro.  If its caged, then logically, one assumes that it can be uncaged and move.

For something like a movable camera in a gimbal, or even a gyroscopic attitude indicator, it means that it is physically locked into place so that it can't move. On the gimbals (such as the camera pod in a predator, or other ISR asset) that can mean the camera is rotated into a stowed position, and then a pin is mechanically moved into place to keep the payload from moving.  This is usually done to prevent damage.
For a gyroscopic attitude indicator, you can generally cage it by pulling out a knob, and rotating it to a specific setting.  Again, this physically locks it into place so that it doesn't move.  This is usually done prior to shutting down as the mechanisms keeping the gyros spinning are powered down.  This is to prevent damage as well as give it a safe position from which to start from when power is re, applied to the aircraft.


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How much lag does an Attitude Indicator experience?
How much lag does an Attitude Indicator exhibit when it is working as designed? Other than well-known problems like tumbling beyond certain limits in pitch and roll, and precession errors from the erecting system, does a gyroscopic AI experience lag that makes it unusable for turbulent or gusty conditions?
Similarly, are there any conditions that would cause an AHRS-based AI to exhibit lag or otherwise show an incorrect indication of the horizon relative to the aircraft?
(Inspired by comments on this answer)

There is no virtually no lag on attitude indicators. The traditional ones are based on a mechanical gyroscope. Due to the gyroscope being gimbaled, it remains in a fixed attitude.
When the aircraft changes attitude, the gyroscope in the attitude indicator remains at its original orientation. When you look at the attitude indicator you are looking basically directly at the gyroscope, packed in a nice horizon displaying wrapping.

The modern attitude indicator in a glass cockpit gets the attitude information from the Attitude and heading reference system (AHRS). There is of course some lag associated with digital data transfer and display refresh rate, but these effects are too tiny to be noticeable by humans.
The first generation of these systems used mechanical gyroscopes as well. Nowadays most AHRSs uses Ring Laser Gyros or Fibre Optic Gyros. These gyroscopes use relativistic effects of light travelling clockwise and counter-clockwise through a circular path. The accuracy of these systems is very high and there is no delay.
Another technology that is used is are Micro-electromechanical Systems (MEMS) gyroscopes. The are based on a vibrating structure. The direction of a vibration tends to remain in the original direction, even though the supporting structure rotates. MEMS are relatively cheap compared to RLG and FOG but they are less accurate. Due to developments in the automotive and mobile telephony industry where attitude sensors are used for various applications the accuracy of MEMS gyroscopes has improved while their costs have decreased. This makes them now interesting for application in avionics.

Do you know if MEMS have tendency to have random drift or systematic drift? Given many enough MEMS devices in a single aircraft, and you average over all sensors, would it be more accurate than RLG or FOG?

Talking about vacuum-driven gyros, which are what I'm mainly familiar with: When everything is working as designed (sufficient air pressure for normal gyro rotor speed, moderate maneuvers) there is some lag.
You'll notice it if you're looking for it, but the "1-2 seconds" mentioned in the linked answer seems on the high side (at least based on what I've seen in light aircraft).
Vacuum-driven attitude indicators lag because of the way they operate: Basically a set of vanes are always trying to pull the gyro upright relative to gravity, and the inertia in those vanes and the air flow induces a slight lag before the rotor (and visual indicator) moves.
That's not the only error in your trusty attitude indicator. Stealing liberally from an old edition of the IFR Handbook for the rest of gory details details:

…
Another group of errors, associated with the design and operating principles of the attitude indicator, are induced during normal operation of the instrument. A skidding turn moves the pendulous vanes from their vertical position, precessing the gyro toward the inside of the turn. After return of the aircraft to straight-and-level, coordinated flight, the miniature aircraft shows a turn in the direction opposite the skid. During a normal turn, movement of the vanes by centrifugal force causes precession of the gyro toward the inside of the turn.
Errors in both pitch and bank indications occur during normal coordinated turns. These errors are caused by the movement of the pendulous vanes by centrifugal force, resulting in the precession of the gyro toward the inside of the turn. The error is greatest in a 180° steep turn. If, for example, a 180° steep turn is made to the right and the aircraft is rolled out to straight-and-level flight by visual references, the miniature aircraft will show a slight climb and turn to the left. This precession error, normally 3° to 5°, is quickly corrected by the erecting mechanism. At the end of a 360° turn, the precession induced during the first 180° is cancelled out by precession in the opposite direction during the second 180° of turn. The slight precession errors induced during the roll-out are corrected immediately by pendulous vane action.
Acceleration and deceleration also induce precession errors, depending upon the amount and extent of the force applied. During acceleration the horizon bar moves down, indicating a climb. Control applied to correct this indication will result in a pitch attitude lower than the instrument shows. The opposite error results from deceleration. Other errors, such as "transport precession" and "apparent precession," relate to rotation of the earth and are of importance to pilots and navigators concerned with high speed and long-range flight.

A more common cause of a (noticeable) gyro lag is low vacuum, which results in low rotor speed and makes the entire instrument sluggish.
High vacuum can cause the opposite effect - excessive rotor speed, and "overshoot" in maneuvers.

You can find more of the old IFR handbook over on pilotfriend.com. "IFR Exam-o-Gram #24" available here is also a good read - both of these are from the days when the FAA expected pilots to cram pretty extensive systems knowledge into their brains.
The gyro vanes picture above is out of the Airframe mechanic's handbook - AC 65-15A which is actually still current.

It should be mentioned that these days all airliners use inertial reference systems with set of laser gyroscopes or vibrating structure gyroscopes and digital processing that are significantly more precise and their lag is measured in milliseconds, so while this is all true for average private aircraft, it does not apply to airliners.

@JanHudec I'm sure there's an old MD-80 or 737-200 flying around somewhere with a vacuum attitude indicator, but yes: most modern airliners will be using more sophisticated gyroscopes that don't suffer from these errors. (For that matter I think electric spinning-mass gyros are less susceptible to these errors than air-driven gyros, though I believe they have some different quirks...)

Re "Vacuum-driven attitude indicators lag because of the way they operate: Basically a set of vanes are always trying to pull the gyro upright relative to gravity, and the inertia in those vanes and the air flow induces a slight lag before the rotor (and visual indicator) moves." -- I'm not sure this is true. The gyro stays stationary while the airplane moves around it. Inertia of stuff attached to the gyro would not increase "lag". In banked turning flight, where the gyro should not be aligned with "apparent down", the action of the vanes causes a very slight error, but not really a "lag".

All traditional instruments have a certain amount of lag. This is one of the factors that complicates flight automation. Certain advanced instruments such as inertial measurement units and ring laser gyroscopes have no lag.
You can find details on the typical lag and other issues with the artificial horizon ("attitude indicator") in any instrument flying textbook, or web site, such as this one. Any prolonged non-level flight will produce an error in the AI, and for this reason IFR holding patterns have a one-minute level flight leg after each minute of turn. This extra travel distance gives the AI the time to return to normal.

MEMS vibrating-structure gyros should also have negligible lag (if any)

You'd be surprised how much lag the average human has between receiving signals and becoming aware of them. Our mind filters the delay out, but it can be measured (between 0.1 and 0.2 s) and is in most cases higher than the delay of well-designed automatic systems.

the level flight in the holding pattern is to help ATC: in this way they know that it takes you 4 minutes to complete a loop and they schedule accordingly.

W/ traditional mechanical gyros-- doing a 30-degree banked left turn for 20 minutes straight should introduce no more error than do thing the same for 5 minutes.  In general, the (very slight) error will be greatest after 180 degreees of turn and back to zero after 360 degrees of turn, it doesn't keep accumulating indefinitely.  (Though after many circles I wouldn't bet money that the point of max error is still exactly 180 degrees after the original point of entry.)  Anyway your statement about the purpose of the straight legs in the holding pattern can't be right.

I have read several times that a skidding turn will somewhat increase the error during a turn, but I found this extremely suspicious since a gyroscope is basically “always in a skidding turn”. Indeed, the gyroscope is supposed to be mostly vertical at all times and has no idea what the aircraft is doing around it. In other words the aircraft moves around a fixed gyroscope and the gyroscope take turns with no concept of skidding from the perspective of the aircraft.

a) This is probably going to be deleted for not really being an answer.  b) I think an argument can be made that for any given bank angle, the gyro's "self-erecting" mechanism, which tries to align the gyro with the direction of the "felt" G-loading, introduces more error in a skid.  (It would introduce zero error in a slip that was so pronounced the turn rate was zero, and thus there was no "centrifugal force".)  But, you also get around the turn faster when skidding than when coordinated, so for a given turn rate the error might not be more in the skid.

At the end of the day it's not going to matter much, because the error accumulates very slowly, and also because by the time you've turned 180 degrees the erecting mechanism starts taking out whatever error it's had time to put in, and after 360 degrees of turn the net effect should be zero, skidding or not.  Could be grounds for a new question though: "after exactly 180 degrees of turn, is error in displayed bank angle greater if skidding than if coordinated-- give answers for given constant bank angle and also for given constant turn rate."

This post does not answer the stated question.


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How can I find our FAA airport designation number?
Several years ago we were issued an airport designation number by the FAA. The information was lost when my father died. How do I find out what our designation number is?

Runways are numbered according to magnetic heading.  I'm not aware of other designation numbers.

Can you explain what you mean by "runway designation number"? And which airport are you talking about, i.e. what's the airport code?

Do you mean airport identifier rather than runway designation?  If you can give the location of the runway (lat/lon, reference to a city, name, etc) we might be able to find it.

@Pondlife I think the airport code is exactly what he's looking for.

What you're looking for is the FAA Airport/Facility Directory (A/FD). You can search it on the FAA A/FD Advanced search page. If your runway is registered as an airport with the FAA, its airport identifier will be in the A/FD. It will also include the runway numbers (there will be one for each end of the runway,) as well as other information about the runway (surface type, exact heading, altitude, etc.) See How are runways numbered? for more information on runway numbers. Another website available for searching A/FD information is airnav.com.
Another way to find information on the airport is to look at a Sectional Chart. For most private airports, an 'R' with a circle around it will appear where your runway is located and it will have the name of the airport beside it. You can then use that name to look it up in the A/FD. Skyvector.com is an easy way to look at sectional charts. It works a lot like Google Maps, except that it shows you the FAA sectional chart for your area rather than a normal map. You can just zoom in on your area to find the airport marker.
Your airport will look something like the one that I've circled in red on this sectional chart image:

If your runway has a hard surface (i.e. it's paved with asphalt or concrete) and is more than 1,500 feet long, it might look like the airport circled in the picture below rather than having the circled 'R'. In this picture, the purple circle indicates the airport and the white line within the circle indicates the location and orientation of the runway.

Search directly on the FAA page.


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What's the minimum timeline for fixing the issues/finding from NTSB/FAR?
When air-crash investigation completes, either NTSB/FAR/other investigating agency finds some issue with instruments/equipments. What is the minimum timeline given to instrument/equipment manufacturer to fix the issue? (May be based on the severity of the issue).

Note that FAR is Federal Aviation Regulations which is a list of rules published by the FAA, it's not an agency/investigative body/etc. Just a big stack of paper. The FAA (Federal Aviation Administration) is the one responsible for producing FAR, and they are the CAA for the USA (as noted in Jan's answer).

That is up to the civil aviation authority, which in most countries is distinct agency from the investigation board (in USA this is FAA), to decide.
They will take into consideration how likely the problem is to repeat, how big risk it would be if it does¹ and as secondary criteria how much work the fix is and how much it will cost. What must be done will be published in an airworthiness directive.
If the problem is serious, they will prohibit any further flights except for testing purposes until fix is installed. And remember the fix may not be known yet. For example after the 787 battery fires, FAA published airworthiness directive that prohibited operations until “approved fix is installed” couple of days after the third incident when they just started to discuss what the fix should be with Boeing and whole fleet remained grounded for almost half a year until the modified batteries were ready.
On the other end of the scale a problem may not necessarily result in mandatory change at all. Many issues simply result in mandating additional inspections, shortening intervals between inspections or shortening maximum service life of some component, which may be relaxed again if the manufacturer develops an improved version of the component and the operator installs it, neither of which is mandatory. Even quite severe problems may just be solved with inspections, because most components have inherently limited life and the problem just indicated higher wear then originally anticipated.

¹ It is important to remember that the investigators don't only investigate crashes, but they get reports of all incidents, which means any failure where there was elevated risk. They then investigate those where they consider the risk significant or that are more common then expected. So often things are investigated where the probability of fatal outcome is low. In such cases the investigators will only consider safety and will publish a safety recommendation, but the aviation authority has to also consider other practical aspects and may choose not to enforce it.

It's also important to remember that NTSB often makes a lot of recommendations after an investigation is concluded, but that the NTSB's pronouncements are just that - non-binding recommendations. Many airlines adopt some or all of these recommendations, but nothing requires them to do so unless the FAA passes a regulation mandating action (a change to Part 91/121/135, an airworthiness directive, etc.)

It would depends on various factors.
First is the severity of the issue. If it can cause a accident then the entire fleet of affected aircraft will be grounded until the fix has been certified and installed.
If the issue is not that severe then it will depend on how hard the fix is to install. The harder/more time consuming it is the more time is given. Some fixes can be put in during the normal pre-flight check.
Then they will give enough time for the fleet to get cycled through the scheduled more extensive A or B checks where the fix will get installed.


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Is it possible to fly with counterbalanced single blade engines?
Refer the image for counterbalanced single blade (Source http://www.aviastar.org/helicopters_eng/bo-103.php).
In ground school, they took us for aircraft inspection at end of our ground school classes. The instructor told us that "counterbalanced single blade engines" are efficient.
I have 2 questions here

Why development under these fields are stopped (Bo-102/103)?
How Single blade will be efficient than 2 blades rotor-craft engines?

See http://i1.wp.com/www.ladieslovetaildraggers.com/wp-content/uploads/2013/10/J2-Cub-Single-blade-prop.jpg and https://www.reddit.com/r/flying/comments/1ui1bu/a_real_and_working_single_bladed_propeller/

Both Bo-102 and 103 were experimental aircraft, with Bo-102 more of a jig than an actual aircraft. They were used a testbed for various technologies and the single blade rotor is only one of them , with the main thrust being in the development of (hinge-less) rigid rotor and (glass fiber reinforced) composite blades.
The single blade rotor offers some advantages over the (normal) multi-blade configurations like,

The blade passes through 'clean' air and is thus more efficient compared to the multi-blade configurations, where the (following) blade passes through the turbulent (wake) air from the previous blade, at-least in hover.
The single blade propeller is compact and for this reason, is used in some self launching gliders which fold their propellers inside their fuselage,like the Alisport Silent 2 Targa.

However, there are significant problems associated with this design,which makes it (mostly) unsuitable for widespread use.

For reducing vibrations, the blade has to be counterbalanced by a mass, which is practically dead weight. While this may be acceptable for small and lightweight propellers used in gliders, this is a major problem in helicopter blades, which are significantly heavier. For example, the Mi-17 Main Rotor Blade weighs ~140 kg.
If the mass is  kept low, the lever arm is huge and this increases drag.
Though the blade may be  balanced at the pitch axis (to reduce vibrations), torque induced in the rotor blade (due to lift) will cause significant vibrations. As the torque is increased, if the weight is fixed, the rotor will tend to rotate the engine and rip it off. The only way to prevent this is to balance the blade, both aerodynamically and centrifugally, which is easier said than done.
The same problem arises as the drag of the blade is different from that of the mass arm, with a torque being created parallel to the axis of rotation.
The rotor blades usually 'cone' in flight; this means that the lift vector is slightly tilted towards the center, not concentric with the rotor plane.
The blade has aerodynamic forces acting on it while the balance weight does not. Due to this, the precess differently, which causes unbalance and vibration.

It might be helpful to clarify what you mean by the third point.  Are you talking about torque parallel to the axis of rotation (caused by blade having more drag than the counterweight) or torque perpendicular to the axis of rotation (caused by the fact that the blade produces lift and the counterweight doesn't).  If you're talking about both, I think it might be clearer to split them into separate bullet points.

@supercat I'm talking about the torque perpendicular to the axis of rotation (due to lift). It is more severe and varies with changing lift, though various measures were proposed to overcome this problem.

The number of blades determine the solidity ratio of a propeller. If you need to limit tip speed and propeller diameter, the propeller will have a high solidity ratio by using many, short blades. Take a ship's propeller: It needs to work in the space between the draft of the ship and the waterline, so it will have many stubby blades.
If space allows, a bigger propeller has a better efficiency because it  can use a larger mass of air for lift creation. If the propeller has a low advance ratio, the wake of one blade might interfere with the next, so packing more blades will increase the risk of interference. The fewer blades you need for lift (or thrust) creation, the better. Efficiency generally runs inverse to the number of blades.
A single bladed propeller or rotor needs a counterbalance, which in effect is a dead weight. When the interference between two blades is low enough and the disc loading of the rotor is not too low, a two-bladed rotor will be the better choice. Disc loading is the lift relative to the area of the rotor disc and dictates the chord of the rotor blade(s) once their number is defined. Only when structural limits will make the chord of an ideal two-bladed rotor too short will a single-bladed rotor be attractive.


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Why did the crashed TAM Airlines Flight 3054 veer off the runway only near the end?
For the accident, why did the aircraft veer off the runway near the end of the runway, instead of the moment it touched down (where the left engine went into reverse thrust and the right engine powered up to climb throttle)?
The aircraft managed to maintain a (relatively) straight path for most of the runway length. I thought asymmetrical thrust that significant would immediately send it off course

Right Engine thrust
The engine takes about 12 seconds to spool up from idle to full thrust.
Auto-throttle had held both engines near idle during the approach to touchdown. The throttle levers should both be retarded from "climb" to "idle" position prior to touchdown. But only in the last two seconds before touchdown, after the aircraft emitted a warning, was the left throttle retarded - but the right throttle lever was not moved from the "climb" position.
When the left throttle lever was retarded, this disengaged auto-throttle, so  the right engine started to spool up to "climb" power setting as commanded on the right throttle lever.
So immediately after landing the right engine wasn't producing any thrust.
The thrust only developed gradually during the following 12 seconds as the aircraft traveled down the runway.
Rudder authority
At landing the aircraft might be travelling at 140 knots. At this speed, deflection of the rudder by the pilot can still have significant effect and can counteract asymmetric engine thrust.
As the aircraft traveled down the runway, airspeed would have reduced and rudder authority gradually diminish at the same time as the right engine was spooling up to CL (climb) power.
The aircraft ran off the runway at about 90 knots.
Nosewheel steering
When using the rudder pedals for nose wheel steering, the steering angle starts to reduce at 40 knots and progressively reduces to zero degrees at 130 knots.
According to the accident report,

When the accident happened, the volume of precipitation was 0.6 mm.

So a combination of speed and a wet runway may have reduced the effectiveness of nosewheel steering.
I don't know, but I suspect that nosewheel steering may not be able to fully compensate for the yawing effect of left engine at idle and right engine at climb power.
Differential braking

The FDR also recorded the use of the rudder and the differential braking by the pedals as the aircraft veered to the left (probably in an attempt to maintain the plane on the runway and stop it).

It seems that the crew really needed to shutdown or idle the right engine to complete a landing within the boundary of the runway.

The effectiveness of nosewheel steering depends a lot on c.g. position. With a c.g. near the rear limit it would likely be overpowered by asymmetric thrust.

@PeterKämpf Are you saying that the accident aircraft was near the aft limit at the time of landing, so this was a factor?

@Lnafziger: No, all I am saying that without knowledge of the cg position it is hard to know whether nose wheel steering was effective or not.

I think 12 seconds spool up time is a good number for a A320 at ground-idle whilst standing still, but not when the engine is in flight-idle and moving at 140 knots. In the latter case, I would expect the engine to spool up within a few seconds. I believe the maximum allowable time in certification is 8 seconds.